Excavation and foundations are most important when restructuring the grounds or in preparation for a new building to be developed. This is a crucial stage of planning as it denotes where and how the building will grow and stand the test of time ( get this wrong and it will show for ever). A number of tests are carried out upon the proposed site ranging from soil, environmental impacts, water table and drainage to name but a few.
Structural surveys are carried before hand, and in some cases a full topographical survey will be done to ensure accuracy.
Graeme Kelly, Somerset